is there any way to randomize velocities in Reaper?

All I'm seeing are a couple of the included JS plugins that will do it for you (MIDI Tool and MIDI Tool II), nothing built right into Reaper. Assuming those do the trick for you, but you don't want all the MIDI on a track randomized, don't forget that you can also drag effects onto the MIDI items individually.

Edit: Or what he said. :P
 
All I'm seeing are a couple of the included JS plugins that will do it for you (MIDI Tool and MIDI Tool II), nothing built right into Reaper. Assuming those do the trick for you, but you don't want all the MIDI on a track randomized, don't forget that you can also drag effects onto the MIDI items individually.

Edit: Or what he said. :P

As Phils said, select the notes (Ctrl + A selects all of them) and hit "H" on the keyboard. Humanize window pops up